The manufacture of semiconductor-based light-emitting devices such as organic light-emitting diodes (OLEDs) has been commercialized, and such light-emitting devices can be readily manufactured using techniques of mass production. OLEDs are widely used in displays, for example, in mobile phone displays, camera displays, television displays, etc. However, the use of OLEDs in lighting applications such as home or commercial lighting is not widespread owing to various barriers in realisation. For example, even though the use of OLEDs might now be affordable option, it has proven difficult to incorporate them in lighting applications. The actual deploying of an OLED in a luminaire is not a straightforward matter. This is partially owing to the essentially planar shape of an OLED, which necessitates a flat or planar luminaire, which may not be regarded as practical or attractive.
Also, the conductive properties of the materials used in an OLED are generally relatively poor, and techniques for improving the conductivity—and therefore also the light homogeneity across the active layer—are often associated with an increase in device thickness or a decrease in the transparency of a layer through which the light should be emitted. Furthermore, a “large” OLED typically requires more than two electrode contact regions. For example, an OLED might have several anode contact regions and several cathode contact regions, in order to improve the voltage distribution across the active layer. In the known approaches, all contact regions for an electrode are electrically connected together using external circuitry with the aim of improving the electrode conduction characteristics. This requires additional expensive circuitry and additional manufacturing steps.
Any OLED incorporated in a luminaire must be enclosed to protect the fragile substrate and to ensure that the active layer and the electrodes are protected from moisture and the effects of corrosion. Such a dedicated frame or cover for a luminaire adds to the overall cost. Furthermore, it may be desired to have a luminaire that emits light on both sides. However, an OLED that emits on both sides, for example a transparent OLED or TOLED, requires more investment at manufacturing level, for example a dedicated production line, so that a luminaire using such OLEDs would be prohibitively expensive.
Therefore, it is an object of the invention to provide a more straightforward and economical luminaire using semiconductor light-emitting devices.